The polyamide nylon-12 (PA-12), because of its remarkable mechanical properties and its resistance to petrol, oil and greases is widely used in motor vehicles and heavy goods vehicles. Because of the developments in engines and a change in their environment, there is now a requirement for thermoplastics that can be used at temperatures of 20 to 30° C. above the operating temperatures of PA-12, while still maintaining good flexibility, impact strength, chemical resistance and good convertibility in extrusion. Polyamides having a higher melting point than PA-12 are known, such as for example PA-6, PA-6,6, PA-4,6, PA-6,10, PA-6,12 and PA-10,10. However, the problem not solved at the present time is that these pure PAs are not flexible enough.
Patent EP 1 038 921 describes polyamide-based thermoplastic compositions comprising, by weight:
50 to 99% of a polyamide;
1 to 50% of a catalyzed polyamide;
0 to 40% of a plasticizer;
0 to 60%, preferably 0 to 30%, of a flexible modifier;
the total being 100%.
These compositions are useful for manufacturing, for example, flexible hoses. The examples relate only to PA-11 and PA-12, but other homopolyamides and copolyamides are mentioned in the description.
Patent Application US 2002-0019477 describes, in the examples, moulding materials comprising PA-6,12 with acid end groups, PA-6,12 with amine end groups, a grafted EPR (grafted by maleic anhydride), an ethylene/alkyl acrylate/glycidyl methacrylate copolymer and a plasticizer (BBSA). Other homopolyamides and copolyamides are mentioned in the description.
Patent Application US 2002-0082352 describes polyamide-based compositions to be used in multilayer structures. The examples describe compositions comprising high-viscosity PA-12, a polyamine/polyamide copolymer and either a grafted SEBS or a blend of an ethylene/propylene block copolymer and of a grafted polypropylene. Other homopolyamides and copolyamides are mentioned in the description.
Patent Application US 2002-0119272 describes polyamide-based compositions to be used in multilayer structures. One of the layers comprises:
a polyamide chosen from PA-6, PA-6,6 and PA-6/6,6;
a polyamine-polyamide;
optionally, a polyamide chosen from PA-11, PA-12, PA-6,12, PA-10,12 and PA-12,12.
A composition has now been found that is based on a polyamide resulting from the chain linking of a diamine having from 6 to 10 carbon atoms, of a diacid having from 10 to 12 carbon atoms and, optionally, of at least one monomer chosen from lactams, α,ω-aminocarboxylic acids, diamines and diacids, this composition being able to be used at temperatures of 20 to 30° C. above the operating temperatures of PA-12, while still maintaining good flexibility, impact strength, chemical resistance and good convertibility in extrusion.